Ok I have this strange issue. When I minimize a window there have been few times in which the X reboots. Go to a TTY and then appears the GDM login screen. First I thought it was all about Firefox 3 beta (which I'm using now) but this morning happened to me minimizing Evolution, and Pidgin window conversation. It's quite frustrating, because I was uploading a video (350MB) to Veoh and it was in the 96% and then all blew away! I've been digging around and I don't see a cause.

Nothing to say about your specs (powerful though)Which driver for nvidia?I had one such incident I think, I either closed or minimized and suddenly x restartedI have the nvidia driver, not the newest one though (6600 GT PCIX)